Ways to get an idea out of your head and onto a canvas: AI generators, text-to-diagram languages that live in version control, and whiteboards for working with other people.
Paste a paragraph of text and it proposes several visuals for it. The output needs editing, and it beats staring at an empty canvas when you have to illustrate a doc.
Hand-drawn look that makes a diagram feel provisional, so people argue with the idea instead of the styling. Free, no account needed, and it exports cleanly.
Diagrams written as text, rendered by GitHub, GitLab, Notion and most documentation tools without a plugin. The right answer when a diagram must live next to the code and survive review.
A hosted editor for Mermaid with a visual mode and AI generation on top of the same syntax. Useful when part of your team refuses to write markup.
A newer diagram language with much better automatic layout than Mermaid on dense architecture graphs. Fewer integrations, noticeably prettier output.
The original layout engine, still unbeaten for programmatically generated graphs with thousands of nodes. Ugly by default and it will never break your build.
Text-based UML with sequence, class and component diagrams covered properly. Verbose syntax, and the only sensible pick when you need formal UML rather than boxes and arrows.
Free forever, works offline, stores files wherever you want, and has every stencil set you will ever need. It looks dated because it has been reliable for a very long time.
Flowcharts, wireframes and mind maps that snap into place with almost no fiddling. Product managers love it because it is fast and hard to make ugly.
The infinite whiteboard for workshops, retros and sticky-note sessions with a distributed team. It gets slow on very large boards, and the templates carry a lot of meetings.
Figma whiteboard, worth using purely because it sits next to your design files. Lighter than Miro on templates, better if the team already lives in Figma.
A very fast open source canvas that developers embed into their own products. As an end-user whiteboard it is minimal in the good sense.
Docs and diagrams together, aimed squarely at engineering design documents. The AI diagram generation understands cloud architecture vocabulary better than general tools.
The enterprise option, with data linking, permissions and admin controls that IT departments ask about. Heavier than everything else here and it is built for that audience.
Implements the C4 model, so you describe your architecture once and generate every zoom level from it. Niche, opinionated, and excellent if you have adopted C4.